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Resolution

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The camera's light sensitive CCD converts the scene into a grid of pixels that make up a digital photograph. The resolution is the total number of pixels in the photo, for example, one million or 350,000. This is one factor that affects image quality, providing the image that's being formed on the CCD is sharp. CCDs with greater numbers of pixels should have higher resolution. Buying adviceUnless you have a specific need for a low resolution model choose a camera with the highest resolution you can afford. This will enable you to make bigger enlargements.

Related Terms

Cameras offer different levels of image quality which is determined by
lens quality and the resolution (number of pixels) delivered by the CCD. Basic
cameras have VGA resolution CCDs that record images with 640x480 pixels. Next up
are SVGA models that record 800x600 pixels and then the XVGA models that create
pictures with over 1024x768 pixels. The latest super megapixel models go way
beyond these figures – currently creating images up to 3040x2016. If you're
buying the camera to take pictures for use on screen you only need to buy a VGA
model, but if you demand photo quality you need at least a megapixel variety and
even then the quality is only good to about 5x7inch from a normal inkjet
printer.

Many scanners and some digital cameras have two resolution figures quoted in their spec sheets - optical and interpolated. Optical is the figure you should trust as it's a true pixel capture, unlike interpolated that uses the optical figures to calculate and add new pixels to increase resolution.

A digital photo that contains enough pixels per inch to suit the media it will be displayed on. If it's only being viewed on a PC monitor 72dpi is fine (although not high resolution) while an image being printed in a magazine has to be 300dpi.

A format for storing digital photographs at different resolution settings
developed by Kodak. PhotoCD can be order when you have a film processed and the
lab will scan in the negatives and add them to a CD. One CD can hold up to 100 images, each stored in five resolution levels. You're
asked, when opening a picture, what resolution version is
required.

The total number of pixels on a CCD array. This is not
always the best indication of a camera's resolution as some CCD chips have a
number of pixels around the that are only used to ensure the pixels that are
used produce accurate colours. The true indication of a camera's resolution is
the two figures quoted, say 1600x1200, which indicate the CCD's actual output.
"A ... MP camera" is used to describe a model that has a CCD with a certain number times million
pixels, which says something about how big the images are that it can create.

Digital images are made up of square pixels and when the image is low resolution there are fewer pixels per inch. This creates a rough step-like appearance that is most noticeable on diagonal straight edges. This staircase effect is often described as "jagged".

The amount of data held in a file determines its size. High resolution digital images can be 50 megabytes, for instance, while a text document may only be a few hundred kilobytes or less. Images can be compressed to save space, and folders of text
and pictures can be grouped and reduced in size using programmes such as Stuffit, WinRAR or WinZip.

A flexible magnetically-sensitive disc that's held inside a 3.5inch square
hard plastic case. It has a storage capacity of 1.4Mb which is ideal for
transporting text or low resolution or highly compressed digital images. The
format is gradually becoming antiquated as advanced storage options such as
removable media compete.

A digital picture can be enlarged in size by adding new pixels to the
existing grid. Some camera and scanner software do this as the picture is
processed to give higher resolution results. The fact is, interpolation
increases the picture by guessing what pixels are required and uses information
from the surrounding pixels to achieve this. Although the overall picture count
will rise image quality can actually suffer and definition is often reduced.

Unlike resampling here the image size is changed without modifying the resolution. For example if you resized a 10x8in 72dpi photo to 4x6in the dpi would be increased, whereas if you resample youd keep the same dpi.

Cameras with figures in this column have a digital zoom that increases the magnification of the optical lens by the quoted figure. To do this it uses part of the CCD so the resolution is reduced to allow for the increase magnification. If you dont intend making big enlargements this is useful other wise stick to the optical zoom. Most cameras have the option to turn the digital zoom on or off.